FIG. 1 illustrates a prior art igniter which generally comprises a metal shell or body 20 that has a flange or mounting means (not shown) for mounting the igniter to an engine. The shell 20 constitutes one electrode of the igniter plug. A central electrode 30 passes through the shell and is supported by an insulator 40 which surrounds the central electrode 30. The forward end 35 of electrode 30 is isolated from the forward end 24 of the metal shell 20 by an electrically insulating ceramic sleeve 80. The insulator 80 is captivated within the shell 20 by ring 23 and the forward end 24 of the shell 20. In operation an arc is formed between the forward surface 24a of the forward end 24 of the outer electrode 20 and the forward end 35 of the electrode 30. This subjects the insulator 80 to intense heat and it expands. Some igniters also have a semiconductive coating across the front surface 84 of the insulator 80 to facilitate arcing during starting. Operation of the igniter causes the forward end 24a to erode. Eventually the erosion is so great that the ceramic insulator 80 becomes loose and can fall out of the igniter. This, of course, causes the igniter to fail, requiring replacement.